package dag
import (
"encoding/json"
"fmt"
"strconv"
"strings"
"github.com/pkg/errors"
"golang.org/x/crypto/openpgp"
"github.com/MichaelMure/git-bug/entity"
"github.com/MichaelMure/git-bug/identity"
"github.com/MichaelMure/git-bug/repository"
"github.com/MichaelMure/git-bug/util/lamport"
)
// TODO: extra data tree
const extraEntryName = "extra"
const opsEntryName = "ops"
const versionEntryPrefix = "version-"
const createClockEntryPrefix = "create-clock-"
const editClockEntryPrefix = "edit-clock-"
// operationPack is a wrapper structure to store multiple operations in a single git blob.
// Additionally, it holds and store the metadata for those operations.
type operationPack struct {
// An identifier, taken from a hash of the serialized Operations.
id entity.Id
// The author of the Operations. Must be the same author for all the Operations.
Author identity.Interface
// The list of Operation stored in the operationPack
Operations []Operation
// Encode the entity's logical time of creation across all entities of the same type.
// Only exist on the root operationPack
CreateTime lamport.Time
// Encode the entity's logical time of last edition across all entities of the same type.
// Exist on all operationPack
EditTime lamport.Time
}
func (opp *operationPack) Id() entity.Id {
if opp.id == "" || opp.id == entity.UnsetId {
// This means we are trying to get the opp's Id *before* it has been stored.
// As the Id is computed based on the actual bytes written on the disk, we are going to predict
// those and then get the Id. This is safe as it will be the exact same code writing on disk later.
data, err := json.Marshal(opp)
if err != nil {
panic(err)
}
opp.id = entity.DeriveId(data)
}
return opp.id
}
func (opp *operationPack) MarshalJSON() ([]byte, error) {
return json.Marshal(struct {
Author identity.Interface `json:"author"`
Operations []Operation `json:"ops"`
}{
Author: opp.Author,
Operations: opp.Operations,
})
}
func (opp *operationPack) Validate() error {
if opp.Author == nil {
return fmt.Errorf("missing author")
}
for _, op := range opp.Operations {
if op.Author().Id() != opp.Author.Id() {
return fmt.Errorf("operation has different author than the operationPack's")
}
}
if opp.EditTime == 0 {
return fmt.Errorf("lamport edit time is zero")
}
return nil
}
// Write write the OperationPack in git, with zero, one or more parent commits.
// If the repository has a keypair able to sign (that is, with a private key), the resulting commit is signed with that key.
// Return the hash of the created commit.
func (opp *operationPack) Write(def Definition, repo repository.Repo, parentCommit ...repository.Hash) (repository.Hash, error) {
if err := opp.Validate(); err != nil {
return "", err
}
// For different reason, we store the clocks and format version directly in the git tree.
// Version has to be accessible before any attempt to decode to return early with a unique error.
// Clocks could possibly be stored in the git blob but it's nice to separate data and metadata, and
// we are storing something directly in the tree already so why not.
//
// To have a valid Tree, we point the "fake" entries to always the same value, the empty blob.
emptyBlobHash, err := repo.StoreData([]byte{})
if err != nil {
return "", err
}
// Write the Ops as a Git blob containing the serialized array of operations
data, err := json.Marshal(opp)
if err != nil {
return "", err
}
// compute the Id while we have the serialized data
opp.id = entity.DeriveId(data)
hash, err := repo.StoreData(data)
if err != nil {
return "", err
}
// Make a Git tree referencing this blob and encoding the other values:
// - format version
// - clocks
tree := []repository.TreeEntry{
{ObjectType: repository.Blob, Hash: emptyBlobHash,
Name: fmt.Sprintf(versionEntryPrefix+"%d", def.FormatVersion)},
{ObjectType: repository.Blob, Hash: hash,
Name: opsEntryName},
{ObjectType: repository.Blob, Hash: emptyBlobHash,
Name: fmt.Sprintf(editClockEntryPrefix+"%d", opp.EditTime)},
}
if opp.CreateTime > 0 {
tree = append(tree, repository.TreeEntry{
ObjectType: repository.Blob,
Hash: emptyBlobHash,
Name: fmt.Sprintf(createClockEntryPrefix+"%d", opp.CreateTime),
})
}
// Store the tree
treeHash, err := repo.StoreTree(tree)
if err != nil {
return "", err
}
// Write a Git commit referencing the tree, with the previous commit as parent
// If we have keys, sign.
var commitHash repository.Hash
// Sign the commit if we have a key
signingKey, err := opp.Author.SigningKey(repo)
if err != nil {
return "", err
}
if signingKey != nil {
commitHash, err = repo.StoreSignedCommit(treeHash, signingKey.PGPEntity(), parentCommit...)
} else {
commitHash, err = repo.StoreCommit(treeHash, parentCommit...)
}
if err != nil {
return "", err
}
return commitHash, nil
}
// readOperationPack read the operationPack encoded in git at the given Tree hash.
//
// Validity of the Lamport clocks is left for the caller to decide.
func readOperationPack(def Definition, repo repository.RepoData, resolver identity.Resolver, commit repository.Commit) (*operationPack, error) {
entries, err := repo.ReadTree(commit.TreeHash)
if err != nil {
return nil, err
}
// check the format version first, fail early instead of trying to read something
var version uint
for _, entry := range entries {
if strings.HasPrefix(entry.Name, versionEntryPrefix) {
v, err := strconv.ParseUint(strings.TrimPrefix(entry.Name, versionEntryPrefix), 10, 64)
if err != nil {
return nil, errors.Wrap(err, "can't read format version")
}
if v > 1<<12 {
return nil, fmt.Errorf("format version too big")
}
version = uint(v)
break
}
}
if version == 0 {
return nil, entity.NewErrUnknowFormat(def.FormatVersion)
}
if version != def.FormatVersion {
return nil, entity.NewErrInvalidFormat(version, def.FormatVersion)
}
var id entity.Id
var author identity.Interface
var ops []Operation
var createTime lamport.Time
var editTime lamport.Time
for _, entry := range entries {
switch {
case entry.Name == opsEntryName:
data, err := repo.ReadData(entry.Hash)
if err != nil {
return nil, errors.Wrap(err, "failed to read git blob data")
}
ops, author, err = unmarshallPack(def, resolver, data)
if err != nil {
return nil, err
}
id = entity.DeriveId(data)
case strings.HasPrefix(entry.Name, createClockEntryPrefix):
v, err := strconv.ParseUint(strings.TrimPrefix(entry.Name, createClockEntryPrefix), 10, 64)
if err != nil {
return nil, errors.Wrap(err, "can't read creation lamport time")
}
createTime = lamport.Time(v)
case strings.HasPrefix(entry.Name, editClockEntryPrefix):
v, err := strconv.ParseUint(strings.TrimPrefix(entry.Name, editClockEntryPrefix), 10, 64)
if err != nil {
return nil, errors.Wrap(err, "can't read edit lamport time")
}
editTime = lamport.Time(v)
}
}
// Verify signature if we expect one
keys := author.ValidKeysAtTime(fmt.Sprintf(editClockPattern, def.Namespace), editTime)
if len(keys) > 0 {
keyring := PGPKeyring(keys)
_, err = openpgp.CheckDetachedSignature(keyring, commit.SignedData, commit.Signature)
if err != nil {
return nil, fmt.Errorf("signature failure: %v", err)
}
}
return &operationPack{
id: id,
Author: author,
Operations: ops,
CreateTime: createTime,
EditTime: editTime,
}, nil
}
// unmarshallPack delegate the unmarshalling of the Operation's JSON to the decoding
// function provided by the concrete entity. This gives access to the concrete type of each
// Operation.
func unmarshallPack(def Definition, resolver identity.Resolver, data []byte) ([]Operation, identity.Interface, error) {
aux := struct {
Author identity.IdentityStub `json:"author"`
Operations []json.RawMessage `json:"ops"`
}{}
if err := json.Unmarshal(data, &aux); err != nil {
return nil, nil, err
}
if aux.Author.Id() == "" || aux.Author.Id() == entity.UnsetId {
return nil, nil, fmt.Errorf("missing author")
}
author, err := resolver.ResolveIdentity(aux.Author.Id())
if err != nil {
return nil, nil, err
}
ops := make([]Operation, 0, len(aux.Operations))
for _, raw := range aux.Operations {
// delegate to specialized unmarshal function
op, err := def.OperationUnmarshaler(author, raw)
if err != nil {
return nil, nil, err
}
ops = append(ops, op)
}
return ops, author, nil
}
var _ openpgp.KeyRing = &PGPKeyring{}
// PGPKeyring implement a openpgp.KeyRing from an slice of Key
type PGPKeyring []*identity.Key
func (pk PGPKeyring) KeysById(id uint64) []openpgp.Key {
var result []openpgp.Key
for _, key := range pk {
if key.Public().KeyId == id {
result = append(result, openpgp.Key{
PublicKey: key.Public(),
PrivateKey: key.Private(),
})
}
}
return result
}
func (pk PGPKeyring) KeysByIdUsage(id uint64, requiredUsage byte) []openpgp.Key {
// the only usage we care about is the ability to sign, which all keys should already be capable of
return pk.KeysById(id)
}
func (pk PGPKeyring) DecryptionKeys() []openpgp.Key {
result := make([]openpgp.Key, len(pk))
for i, key := range pk {
result[i] = openpgp.Key{
PublicKey: key.Public(),
PrivateKey: key.Private(),
}
}
return result
}
